The concept of an email virus is relatively new. The now infamous ‘I LOVE YOU’ virus is an example of an email virus that caused serious damages to systems using the Microsoft™ Outlook™ email system. In the month of May 2000, about 10 billion dollars worth of damage was attributed to this one email virus alone.
In order to understand how such damages are incurred, consider the way in which this type of virus operates. When activated by opening an infected file attachment, the virus reads an address book and proceeds to send copies of itself as an attachment to email messages addressed to recipients selected from the address book. The infection continues at each recipients' mailbox whenever they open the infected message attachment. Even when a recipient does not activate the virus by opening the attachment, the recipients' mailbox is flooded with copies of the infected email message merely because their email address was in the address book of a correspondent who activated the virus.
Furthermore, because of the coupling of wireless communication systems to email, such viruses may also flood wireless messaging services. Damage to wireless systems occurs when the unsolicited flood of messages exceeds the limited bandwidth capacity of the wireless systems.
Although anti-virus software offers some protection for wireless messaging services from such an attack, there are still needs which cannot be met by such software. The initial attack of a new strain of virus is undetectable to installed virus protection software. The effects of ‘I LOVE YOU’ are an example of this, as are the somewhat less publicized effects of variations thereof, which would defeat virus protection software by randomly changing the subject line of the infected email message sent to carry the virus. To make matters worse, some virus protection software strips infected attachments but then sends the original message without the attachment, as well as a further message indicating that the attachment was deleted, to each recipient of an infected email message, resulting in twice as many email messages flooding the recipients' mailbox. Therefore in some cases, when anti-virus software is active, virus protection software can sometimes increase congestion in a wireless messaging system.